Method of treating a hydrocarbon stream comprising methane, and an apparatus therefor

ABSTRACT

A wet hydrocarbon stream comprising at least methane and water is dried thereby forming an effluent stream and a wet disposal stream. Before drying the wet hydrocarbon stream is cooled by indirectly heat exchanging against the effluent stream followed by indirectly heat exchanging against an auxiliary refrigerant stream. The effluent stream is subsequently passed to a further heat exchanger where the effluent stream is cooled against an evaporating refrigerant stream which is subsequently discharged from the further heat exchanger as a spent refrigerant stream. A refrigerant stream in compressed condition is formed by compressing the spent refrigerant and the auxiliary refrigerant stream that is discharged from the indirectly heat exchanging with the wet hydrocarbon stream, whereby allowing direct heat exchanging between the discharged auxiliary refrigerant stream and the spent refrigerant stream before said compressing.

The present invention relates to a method and apparatus for treating a hydrocarbon stream comprising methane.

Hydrocarbon streams comprising methane can be derived from a number of sources, such as natural gas or petroleum reservoirs, or from a synthetic source such as a Fischer-Tropsch process. In the present invention, the hydrocarbon stream preferably comprises, or essentially consists of, natural gas. It is useful to treat and cool such streams for a number of reasons. It is particularly useful to liquefy the hydrocarbon stream.

Natural gas is a useful fuel source, as well as a source of various hydrocarbon compounds. It is often desirable to liquefy natural gas in a liquefied natural gas (LNG) plant at or near the source of a natural gas stream for a number of reasons. As an example, natural gas can be stored and transported over long distances more readily as a liquid than in gaseous form because it occupies a smaller volume and does not need to be stored at high pressure.

WO2012/000998 discloses a method and apparatus for treating a methane-containing hydrocarbon stream, wherein a wet hydrocarbon stream, before it is de-hydrated in a water removal device, is cooled by indirect heat exchanging against an effluent stream from the water removal device and by indirect heat exchange against an auxiliary refrigerant stream. After the indirect heat exchanging against the wet hydrocarbon stream, the effluent stream is passed to a further heat exchanger where it is cooled against an evaporating refrigerant fraction which is obtained from a part of a source refrigerant stream. The auxiliary stream and the part of the source refrigerant stream are obtained by splitting a source refrigerant stream, obtained from a refrigerant compressor and an ambient heat exchanger, into the auxiliary refrigerant stream and said part of the source refrigerant stream. Spent refrigerant discharged from the further heat exchanger is conveyed back to the refrigerant compressor, optionally via a suction drum, and a discharged auxiliary refrigerant stream, resulting from the auxiliary refrigerant stream after cooling the wet hydrocarbon stream, is passed to a second suction inlet in the same refrigerant compressor, optionally via another suction drum.

The present invention provides a method of treating a hydrocarbon stream comprising methane, the method comprising:

-   -   providing a wet hydrocarbon stream at a first temperature, said         wet hydrocarbon stream comprising at least methane and water;     -   cooling of the wet hydrocarbon stream thereby lowering the         temperature from the first temperature to a second temperature,         wherein said cooling of the wet hydrocarbon stream comprises         indirectly heat exchanging against an effluent stream followed         by indirectly heat exchanging against an auxiliary refrigerant         stream;     -   withdrawing from the wet hydrocarbon stream, in a water removal         device at the second temperature, a wet disposal stream         comprising water from the wet hydrocarbon stream and an effluent         stream comprising the wet hydrocarbon stream from which the wet         disposal stream has been removed;     -   passing the effluent stream to a further heat exchanger, said         passing of the effluent stream to the further heat exchanger         comprising heating the effluent stream by indirectly heat         exchanging against the wet hydrocarbon stream in a wet feed heat         exchanger;     -   cooling the effluent stream in the further heat exchanger by         indirect heat exchanging against an evaporating refrigerant         fraction;     -   cycling a refrigerant in repetitive cycles, wherein a single         pass of the refrigerant through the cycle comprises the         following consecutive steps:         -   providing a refrigerant stream in a compressed condition;         -   passing the refrigerant stream in said compressed condition             through a condenser whereby at least partially condensing             the refrigerant stream in said compressed condition, thereby             forming source refrigerant stream comprising a liquid phase             at a refrigerant temperature and a refrigerant pressure;         -   obtaining the evaporating refrigerant fraction comprising             expanding at least a part of a part of the source             refrigerant stream to a pressure lower than the refrigerant             pressure;         -   passing the evaporating refrigerant fraction to the further             heat exchanger;         -   forming a spent refrigerant from the evaporating refrigerant             fraction by absorbing heat from at least the effluent stream             in the further heat exchanger;         -   discharging said spent refrigerant from the further heat             exchanger;         -   passing said spent refrigerant to a refrigerant compressor;         -   discharging from the refrigerant compressor said refrigerant             stream in compressed condition; wherein during said single             pass the cycle further comprises the following consecutive             steps:         -   splitting the source refrigerant stream into said auxiliary             refrigerant stream and said part of the source refrigerant             stream wherein said auxiliary refrigerant stream comprises             at least a part of said liquid phase;         -   indirectly heat exchanging the auxiliary refrigerant stream             against said wet hydrocarbon stream whereby passing heat             from the wet hydrocarbon stream to the auxiliary refrigerant             stream as part of said cooling of the wet hydrocarbon stream             whereby discharging a discharged auxiliary refrigerant             stream containing said heat from the wet hydrocarbon stream;         -   directly heat exchanging the discharged auxiliary             refrigerant stream with the spent refrigerant being passed             to the refrigerant compressor;         -   forming the refrigerant stream in compressed condition by             compressing the spent refrigerant and the discharged             auxiliary refrigerant stream whereby allowing said direct             heat exchanging before said compressing in each single pass.

In another aspect, the present invention provides an apparatus for treating a hydrocarbon stream comprising methane, the apparatus comprising:

-   -   a supply conduit for providing a wet hydrocarbon stream that         comprises at least methane and water;     -   a wet feed heat exchanger connected to the supply conduit, and         arranged to receive the wet hydrocarbon stream from the supply         conduit, and to lower the temperature of the wet hydrocarbon         stream by indirect heat exchanging against an effluent stream;     -   an auxiliary heat exchanging arrangement arranged to further         lower the temperature of the wet hydrocarbon stream discharged         from the wet feed heat exchanger by indirect heat exchanging         against an auxiliary refrigerant stream;     -   a water removal device, arranged to receive the wet hydrocarbon         stream downstream of the auxiliary heat exchanging arrangement,         and comprising a wet disposal stream outlet for discharging a         wet disposal stream comprising water from the wet hydrocarbon         stream, and a vapour outlet for discharging an effluent stream         comprising the wet hydrocarbon stream from which the wet         disposal stream has been removed;     -   a further heat exchanger provided with a first tube bundle inlet         for receiving the effluent stream from the water removal device,         and a first tube bundle outlet for discharging a cooled         hydrocarbon stream, wherein the first tube bundle outlet is         internally in the further heat exchanger connected with the         first tube bundle inlet via a first tube bundle, and wherein         said first tube bundle is arranged in a heat exchanging         relationship with an evaporating refrigerant fraction inside the         further heat exchanger;     -   first connecting means connecting the vapour outlet of the water         removal device with the first tube bundle inlet of the further         heat exchanger, which first connecting means passes through the         wet feed heat exchanger in indirect heat exchanging interaction         with the wet hydrocarbon stream;     -   a refrigerant circuit arranged to cycle a refrigerant in         repetitive cycles, said refrigerant circuit, when being         considered following the flow of the refrigerant during a single         pass through the refrigerant circuit starting from a discharge         outlet of a refrigerant compressor, comprising:         -   a condenser arranged to receive a refrigerant stream in a             compressed condition and to extract heat from the             refrigerant stream in said compressed condition whereby at             least partially condensing the refrigerant stream in said             compressed condition thereby forming a source refrigerant             stream comprising a refrigerant stream in a compressed             condition and comprising a liquid phase;         -   a first expansion device arranged to receive and expand at             least a part of a part of the source refrigerant stream             thereby obtaining the evaporating refrigerant fraction;         -   the further heat exchanger arranged to receive the             evaporating refrigerant fraction from the first expansion             device, in which further heat exchanger a cooling zone is             provided wherein the evaporating refrigerant fraction is             arranged in indirect heat exchanging contact with at least             the effluent stream in the first tube bundle whereby the             evaporating refrigerant fraction is transformed into spent             refrigerant, said further heat exchanger comprising a shell             outlet to discharge the spent refrigerant from the cooling             zone;         -   a spent refrigerant line connecting the shell outlet to the             refrigerant compressor, the discharge outlet of the             refrigerant compressor arranged to discharge said             refrigerant stream in said compressed condition;         -   a splitter, arranged to split the source refrigerant stream             into the auxiliary refrigerant stream and the part of the             source refrigerant stream, wherein said auxiliary             refrigerant stream comprises at least a part of said liquid             phase;         -   a combiner arranged to bring the spent refrigerant and a             discharged auxiliary refrigerant consisting of the auxiliary             refrigerant discharged from the auxiliary heat exchanging             arrangement together in direct heat exchanging contact,             whereby the auxiliary heat exchanging arrangement is             arranged in the auxiliary refrigerant stream between the             splitter and the combiner, said combiner being between the             auxiliary heat exchanging arrangement and the refrigerant             compressor, wherein said refrigerant stream in compressed             condition contains both the discharged auxiliary refrigerant             stream and the spent refrigerant stream.

The invention will be further illustrated hereinafter, using examples and with reference to the drawing in which;

FIG. 1 schematically represents a first process flow scheme representing a method and apparatus according to embodiments of the invention;

FIG. 2 schematically represents a second process flow scheme representing a method and apparatus according to other embodiments of the invention;

FIG. 3 schematically represents a part of a third process flow scheme representing a method and apparatus according to still other embodiments of the invention.

In these figures, same reference numbers will be used to refer to same or similar parts. Furthermore, a single reference number will be used to identify a conduit or line as well as the stream conveyed by that line. While the invention is illustrated making reference to one or more a specific combinations of features and measures, many of those features and measures are functionally independent from other features and measures such that they can be equally or similarly applied independently in other embodiments or combinations.

The present description concerns removal of a wet disposal stream from a wet hydrocarbon stream in a water removal device, yielding an effluent stream comprising the wet hydrocarbon stream from which the wet disposal stream has been removed.

The effluent stream is intended to be cooled in a further heat exchanger against an evaporating refrigerant stream obtained from a source refrigerant stream. After evaporating, the evaporating refrigerant stream is discharged from the further heat exchanger as a spent refrigerant stream and passed to a refrigerant compressor. An auxiliary refrigerant stream, split-off from the same source refrigerant stream in the same refrigerant circuit as used to further the effluent stream, is used to cool the wet hydrocarbon stream before the wet hydrocarbon stream enters the water removal device. A discharged auxiliary refrigerant stream is obtained from the auxiliary refrigerant stream following said cooling of the wet hydrocarbon stream with the auxiliary refrigerant stream.

The source refrigerant stream is formed from a refrigerant stream in compressed condition. The refrigerant stream in compressed condition is formed by compressing the spent refrigerant and the discharged auxiliary refrigerant stream whereby the auxiliary refrigerant is brought in direct heat exchanging contact with the spent refrigerant as it is being passed to the refrigerant compressor.

An advantage of said direct heat exchanging before the compressing is that any liquid phase that may be present in the auxiliary refrigerant stream is evaporated by the direct heat exchanging against the spent refrigerant stream.

This works best if the temperature of the spent refrigerant is higher than the temperature of the auxiliary refrigerant immediately after the indirectly heat exchanging of the auxiliary refrigerant against the wet hydrocarbon stream and the if the auxiliary refrigerant stream flow rate is less than 10% of the spent refrigerant stream flow rate.

A benefit of this proposed method and apparatus is that the liquid loading on the suction drums is lower due to the direct heat exchanging. Furthermore, that no separate suction drum is needed for the auxiliary refrigerant. By omitting the separate suction drum for the auxiliary refrigerant associated capital expenditure may be avoided.

FIGS. 1 to 3 schematically show process flow schemes for treating a hydrocarbon stream. First will be described some of the basic features common to the embodiments illustrated in FIGS. 1 to 3. Most of these features are not shown in FIG. 3. FIG. 3 illustrates an alternative implementation of the compressor 270 which can be applied in either embodiment of FIGS. 1 and 2.

FIGS. 1 to 3 generally illustrate various embodiments of an apparatus for treating a hydrocarbon stream comprising methane. A supply conduit provides a wet hydrocarbon stream 510, which comprises at least methane and water. A wet feed heat exchanger 545 is connected to the supply conduit and arranged to receive the wet hydrocarbon stream 510 from the supply conduit, and to lower the temperature of the wet hydrocarbon stream 510 by indirect heat exchanging against an effluent stream 560 from a water removal device 525. An auxiliary heat exchanging arrangement 575 is arranged to further lower the temperature of the wet hydrocarbon stream 510 discharged from the wet feed heat exchanger 545, by indirect heat exchanging of the wet hydrocarbon stream 510 discharged from the wet feed heat exchanger 545 against an auxiliary refrigerant stream 250. The auxiliary heat exchanging arrangement 575 may be provided in the form of a water removal heat exchanger.

The water removal device 525 is arranged to receive the wet hydrocarbon stream 510 downstream of the auxiliary heat exchanging arrangement 575. Typically the water removal device comprises a first water removal device inlet 551 to receive the wet hydrocarbon stream 510 through. The water removal device 525 further comprises a wet disposal stream outlet 589 for discharging a wet disposal stream 590 comprising water from the wet hydrocarbon stream 510, and a vapour outlet 559 for discharging an effluent stream 590 comprising the wet hydrocarbon stream from which the wet disposal stream 590 has been removed.

A further heat exchanger 535 is provided, arranged with a first tube bundle inlet 531 for receiving the effluent stream 560 from the water removal device 525. The further heat exchanger 535 is also provided with a first tube bundle outlet 539 for discharging a cooled hydrocarbon stream 540. The first tube bundle outlet 539 is within the further heat exchanger internally connected with the first tube bundle inlet 531 via a first tube bundle 532. The first tube bundle 532 is arranged in a cooling zone within the further heat exchanger 535 in a heat exchanging relationship with an evaporating refrigerant fraction inside the further heat exchanger 535.

The vapour outlet 559 of the water removal device 525 is connected with the first tube bundle inlet 531 of the further heat exchanger 535 via first connecting means 565. The first connecting means 565 passes through the wet feed heat exchanger 545 in indirect heat exchanging interaction with the wet hydrocarbon stream 510.

A refrigerant circuit 200 provides cooling to the further heat exchanger 535. The refrigerant circuit 200 is arranged to cycle a refrigerant in repetitive cycles. When being considered following the flow of the refrigerant during one single pass through the refrigerant circuit 200 starting from a discharge outlet 279 of a refrigerant compressor 270, the refrigerant encounters: a condenser 285, a splitter 245, a first expansion device 225, and the cooling zone in the further heat exchanger 535.

The condenser 285 is arranged to receive a refrigerant stream in a compressed condition and to extract heat from the refrigerant stream in said compressed condition, thereby forming a source refrigerant stream 280 comprising a refrigerant stream in a compressed condition and comprising a liquid phase. The first expansion device 225 is arranged to receive and expand at least a part 220 of a part 210 of the source refrigerant stream 280, thereby obtaining the evaporating refrigerant fraction.

The further heat exchanger 535 is arranged to receive the evaporating refrigerant fraction from the first expansion device 225. The evaporating refrigerant fraction is arranged in indirect heat exchanging contact with at least the effluent stream in the first tube bundle 532 in the cooling zone within the further heat exchanger 535, whereby the evaporating refrigerant fraction is transformed into spent refrigerant. The further heat exchanger comprises a shell outlet 239 to discharge the spent refrigerant from the cooling zone. A spent refrigerant line 240 connects the shell outlet 239 to the refrigerant compressor 270.

The refrigerant compressor 270 comprises at least a first suction inlet 271, and a discharge outlet 279. Optionally, more suction inlets may be available to allow feeding into another stage of compression.

The splitter 245 is provided to split the source refrigerant stream 280 into the auxiliary refrigerant stream 250 and the part 210 of the source refrigerant stream 280. The auxiliary refrigerant stream 250 comprises at least a part of the liquid phase from the source refrigerant stream 280.

This apparatus can be operated in accordance with a method wherein a wet hydrocarbon stream 510 comprising at least methane and water is provided at a temperature equal to a first temperature. The wet hydrocarbon stream 510 is cooled, thereby lowering the temperature from the first temperature to a second temperature. The cooling of the wet hydrocarbon stream 510 comprises indirectly heat exchanging against the effluent stream 560, followed by indirectly heat exchanging in the auxiliary heat exchanging arrangement against the auxiliary refrigerant stream 250. A discharged auxiliary refrigerant stream 265 consisting of the auxiliary refrigerant containing heat from the wet hydrocarbon stream 510 is discharged from the auxiliary heat exchanging arrangement 575.

The cooled wet hydrocarbon stream is then fed to the water removal device 525 though the first water removal device inlet 551. In the water removal device 525 a wet disposal stream 590 comprising water, and optionally comprising mercury, is removed from the wet hydrocarbon stream 510 at the second temperature, resulting in the effluent stream 560, which comprises the wet hydrocarbon stream from which the wet disposal stream 590 has been removed. The wet disposal stream 590 is discharged from the water removal device 525 via wet disposal stream outlet 589, for further treatment (not shown) and disposal (not shown).

The effluent stream 560, containing the wet hydrocarbon stream from which components including water and optionally mercury have been removed, is discharged from the water removal device 525 through the vapour outlet 559, and passed to the further heat exchanger 535 via the first connecting means 565. While passing the effluent stream to the further heat exchanger 535, the effluent stream is heated in the wet feed heat exchanger 545, by indirect heat exchange between the effluent stream 560 and the wet hydrocarbon stream 510 prior to admission of the wet hydrocarbon stream 510 into the water removal device 525. Subsequently, the effluent stream 560 is cooled in the further heat exchanger 535 by indirect heat exchanging against the evaporating refrigerant fraction.

To provide this cooling in the further heat exchanger 535, a refrigerant is cycled in repetitive cycles, wherein a single pass of the refrigerant through the cycle comprises the following consecutive steps: providing a refrigerant stream in a compressed condition; and passing the refrigerant stream in said compressed condition through the condenser 285, whereby at least partially condensing the refrigerant stream in said compressed condition, thereby forming the source refrigerant stream 280. The source refrigerant stream 280 comprises a liquid phase at a refrigerant temperature and a refrigerant pressure.

In addition to the effluent stream 560, a part 210 of the source refrigerant stream 280 is passed to the further heat exchanger 535 as well. The evaporating refrigerant fraction is obtained by at least expanding at least a part 220 of the part 210 of the source refrigerant stream 280, to a pressure lower than the refrigerant pressure. The evaporating refrigerant fraction then is passed to the further heat exchanger 535, where the spent refrigerant is formed from the evaporating refrigerant fraction by absorbing heat from at least the effluent stream in the further heat exchanger 535. The spent refrigerant is discharged from the further heat exchanger 535 and passed to the refrigerant compressor 270. The refrigerant compressor 270 discharges said refrigerant stream in compressed condition from the discharge outlet 279 of the refrigerant compressor 270.

In each said single pass of the refrigerant through the refrigerant circuit 200, the cycle further comprises the following consecutive steps: splitting the source refrigerant stream 280 into said auxiliary refrigerant stream 250 and said part 210 of the source refrigerant stream 280; and indirectly heat exchanging the auxiliary refrigerant stream 250 against the wet hydrocarbon stream 510 in the auxiliary heat exchanger arrangement 575.

The splitting is such that the auxiliary refrigerant stream 250 comprises at least a part of the liquid phase from the source refrigerant stream 280. During the indirectly heat exchanging of the auxiliary refrigerant stream 250 against the wet hydrocarbon stream 510 heat passes from the wet hydrocarbon stream 510 to the auxiliary refrigerant stream 250. A discharged auxiliary refrigerant stream 265, which contains heat from the wet hydrocarbon stream 510, is discharged from the auxiliary heat exchanger arrangement 575.

It is presently proposed to bring the discharged auxiliary refrigerant stream 265 and the spent refrigerant stream 240 into direct heat exchanging contact by injecting the discharged auxiliary refrigerant stream 265 into the spent refrigerant stream 240 that is being passed from the further heat exchanger 535 to the refrigerant compressor 270. A combiner 266 may be provided, to bring the spent refrigerant 240 and the discharged auxiliary refrigerant 265 together in direct heat exchanging contact, such that the auxiliary heat exchanging arrangement 575 is arranged in the auxiliary refrigerant stream 250 between the splitter 245 and the combiner 266. The combiner 266 is arranged between the auxiliary heat exchanger arrangement 575 and the refrigerant compressor 270. This allows for directly heat exchanging the discharged auxiliary refrigerant stream 265 with the spent refrigerant 240 being passed to the refrigerant compressor 270, and forming of the refrigerant stream in compressed condition by compressing the spent refrigerant 240 and the discharged auxiliary refrigerant stream 265.

Said directly heat exchanging is allowed before said compressing in each single pass of the refrigerant through the refrigerant circuit 200. Thus, the refrigerant stream in compressed condition is formed by compressing both the (discharged) auxiliary refrigerant stream 250 (265) and the spent refrigerant stream 240.

Direct heat exchanging, as opposed to indirect heat exchanging, involves bringing the two stream in physical contact with each other whereby the two streams are mixed to form a single combined stream.

Preferably, the wet hydrocarbon stream 510 is also passed through a wet feed ambient heat exchanger 585, before being fed to the wet feed heat exchanger 545. The wet feed ambient heat exchanger 585 is suitably provided in the supply conduit. In the wet feed ambient heat exchanger 585, wet hydrocarbon stream 510 may be heat exchanged against ambient. If the optional wet feed ambient heat exchanger 585 is employed, the first temperature is controlled by heat exchanging against an ambient stream, such as for instance an air stream or a water stream. The first temperature may be within 10° C. from ambient temperature. For the purpose of the present disclosure, ambient temperature is the temperature of the air stream or the water stream against which the wet hydrocarbon stream 510 is heat exchanged. Ambient temperature may for instance lie in the range of from 0 to 50° C.

There is essentially no separate other heat exchanger present between the optional wet feed ambient heat exchanger 585 and the wet feed heat exchanger 545, such that the wet hydrocarbon stream 510 can be provided at the temperature equal to the first temperature. No heat exchanging with another medium will be taking place between the optional wet feed ambient heat exchanger 585 and the wet feed heat exchanger 545, other than de-minimis unavoidable heat exchanging with the environment via the piping used for the supply conduit 510 downstream of the wet feed ambient heat exchanger 585. The temperature of the wet hydrocarbon stream as it passes into the wet feed heat exchanger 545 is therefore essentially equal to the first temperature, which is the temperature of the wet hydrocarbon stream as it is discharged from the wet feed heat exchanger 585. In practice this may mean that the temperature of the wet hydrocarbon stream as it passes into the wet feed heat exchanger 545 is less than 5° C. different, preferably less than 2° C. different, from the first temperature.

Preferably, the refrigerant condenser 285 is provided in the form of an ambient heat exchanger. This allows for condensing of the refrigerant stream in compressed condition by heat exchanging the refrigerant stream in compressed condition that is discharged from the refrigerant compressor 270 against ambient. Thus, the source refrigerant stream 280 is conveniently provided at a refrigerant temperature equal to a third temperature, which is within 10° C. from the first temperature.

Optionally, further heat exchanger 535 is further provided with at least one second tube bundle inlet 211, for receiving the part 210 of the source refrigerant stream 280, and at least one second tube bundle outlet 219. The optional at least one second tube bundle outlet 219 is internally in the further heat exchanger 535 connected with the second tube bundle inlet 211 via a second tube bundle 212 arranged in and passing through the cooling zone. This way the second tube bundle 212 is arranged in a heat exchanging relationship with the evaporating refrigerant fraction inside the further heat exchanger 535 in a similar way as the first tube bundle 532. At least one cooled refrigerant stream 220 can thus be discharged from the at least one second tube bundle outlet 219.

With such an optional second tube bundle 212 present, second connecting means may be provided connecting the condenser 285 with the second tube bundle inlet 211. Preferably, the second connecting means is essentially free from any separate heat exchanger. In such embodiments, both the effluent stream 560 and the part 210 of the source refrigerant stream 280 can be cooled in the further heat exchanger 535 by indirect heat exchanging against the evaporating refrigerant fraction 230.

With the indirectly heat exchanging in the wet feed heat exchanger 545 between the effluent stream 560 and the wet hydrocarbon stream 510 it is achieved that the temperature of the effluent stream 560 is restored, within the limits of the approach temperature of the wet feed heat exchanger 545, to better match the temperature of the wet hydrocarbon stream 510. Thus, the heating of the effluent stream 560 by indirectly heat exchanging against the wet hydrocarbon stream 510 in the wet feed heat exchanger 545 during passing of the effluent stream 560 to the further heat exchanger 535, the temperature of the effluent stream 560 is matched to the first temperature as close as the warm end approach temperature of the wet feed heat exchanger 545.

This way, the temperature difference between the effluent stream, suitably in the form of “dried hydrocarbon feed gas”, and the refrigerant stream is substantially the same, such as the same within the approach temperature of the wet feed heat exchanger 545—for instance within 10° C. or preferably within 5° C.—as the temperature difference between the original wet hydrocarbon stream and the source refrigerant stream 280, regardless of the temperature conditions in the water removal device 525.

As a result, any pinching and thermal stress that may be induced in the further heat exchanger 535 when the effluent stream and the refrigerant streams are fed into such further heat exchanger 535 would not be significantly worse than would be the case if the wet hydrocarbon stream would be passed to the further heat exchanger without having passed through the water removal device 525.

Preferably, the wet hydrocarbon stream 510 and the source refrigerant stream 280 may have substantially the same temperature, for instance within 10° C. from each other, preferably within 5° C. from each other. This can for instance be achieved by heat exchanging both the wet hydrocarbon stream and the refrigerant stream against ambient.

However, in addition to the indirect heat exchanging between the effluent stream 560 from the water removal device 525 and the wet hydrocarbon stream 510, the resulting cooled wet hydrocarbon stream is indirectly heat exchanged against the auxiliary refrigerant stream 250 in the auxiliary heat exchanging arrangement 575. Since the temperature of the wet hydrocarbon stream entering the auxiliary heat exchanging arrangement 575 is lower than the first temperature, due to the heat exchanging in the wet feed heat exchanger 545, the temperature of the auxiliary refrigerant stream as it is discharged from the auxiliary heat exchanging arrangement 575 will also be lower than the first temperature. As the auxiliary refrigerant passes from the splitter 245 to the auxiliary heat exchanging arrangement 575 in each single pass the auxiliary refrigerant stream 250 may be expanded in a second expansion device 255. Herewith, it is achieved that, during each single pass of the refrigerant through the refrigerant circuit 200, the auxiliary refrigerant stream 250 is expanded after the splitting in splitter 245 and before the indirectly heat exchanging of the auxiliary refrigerant stream 250 against the wet hydrocarbon stream in the auxiliary heat exchanging arrangement 575. FIGS. 1 and 2 show a Joule-Thomson valve in line 250 as the second expansion device 255.

More heat may be extracted from at least one of:

-   -   the wet hydrocarbon stream in or after the wet feed heat         exchanger 545;     -   the effluent stream 560 in or before the wet feed heat exchanger         545;     -   the wet hydrocarbon stream 510 in the water removal device 525;         by heat exchanging, preferably indirectly heat exchanging. This         way the wet hydrocarbon stream is further cooled down, and/or         its temperature further lowered.

The wet hydrocarbon stream 510, as well as the dried effluent stream 560, contains methane. The wet hydrocarbon stream 510 may be obtained from natural gas or petroleum reservoirs or coal beds. As an alternative the hydrocarbon stream may also be obtained from another source, including as an example a synthetic source such as a Fischer-Tropsch process. Preferably the hydrocarbon stream comprises at least 50 mol % methane, more preferably at least 80 mol % methane.

Depending on the source, the wet hydrocarbon stream may contain varying amounts of other components, including one or more non-hydrocarbon components other than water, such as N₂, CO₂, Hg, H₂S and other sulphur compounds; and one or more hydrocarbons heavier than methane such as in particular ethane, propane and butanes, and, possibly lesser amounts of pentanes and aromatic hydrocarbons. Hydrocarbons with a molecular mass of at least that of propane may herein be referred to as C₃+ hydrocarbons, and hydrocarbons with a molecular mass of at least that of ethane may herein be referred to as C₂+ hydrocarbons.

If desired, the wet hydrocarbon stream 510 may have been pre-treated to reduce and/or remove one or more of undesired components such as CO₂ and H₂S, or have undergone other steps such as pre-pressurizing or the like. Such steps are well known to the person skilled in the art, and their mechanisms are not further discussed here. The composition of the wet hydrocarbon stream thus varies depending upon the type and location of the gas and the applied pre-treatment(s).

The wet feed heat exchanger 545 may be provided in the form of a tube in shell type heat exchanger or pipe in pipe heat exchanger, but preferred is a plate-type heat exchanger such as a plate-fin heat exchanger and/or a printed circuit heat exchanger, optionally in a cold box. Preferably, the wet feed heat exchanger 545 may be installed in a counter current operating mode. In particular, the second outlet 569 may be located on the same heat exchanging side of the wet feed heat exchanger 545 as the first inlet 541 while the second inlet 561 may be located on the same heat exchanging side of the wet feed heat exchanger 545 as the first outlet 549. The second outlet discharges to the first inlet 531 of the further heat exchanger 535. The further heat exchanger 535 is preferably embodied in the form of a coil-wound heat exchanger.

Additionally, the further heat exchanger 535 is provided with a shell inlet 231 to provide access to the cooling zone. The second tube bundle outlet 219 may be connected to the shell inlet 231 via lines 220 and 230 which are connected to each other via the first expansion device 225, which is here shown in the form of a Joule-Thomson valve.

The refrigerant may be a single-component refrigerant such as propane, but is preferably a multicomponent refrigerant. For example, the multicomponent refrigerant may contain a mixture of hydrocarbon components including one or more of pentanes, butanes, propane, propylene, ethane, and ethylene.

The refrigerant condenser 285 may for example be provided in the form of an air cooler or a water cooler. The wet feed ambient heat exchanger 585 is preferably provided in the same form as the refrigerant condenser 285. The refrigerant compressor 270 together with the refrigerant condenser 285 provides the refrigerant source stream 280 in the form of a compressed and ambient cooled refrigerant stream in line 280. The temperature of the source refrigerant stream 280 is equal to a third temperature, preferably at a value within 10° C. from the first temperature, which is the temperature at which the wet hydrocarbon stream 510 is discharged from the wet feed ambient heat exchanger 585.

Spent refrigerant in line 240 is preferably conveyed back to the refrigerant compressor 270 via a suction drum 263. The suction drum 263 may be provided in the form of a phase separator to remove any remaining liquids 269 from the refrigerant compressor feed stream 268 which is fully vaporous.

The wet feed heat exchanger 545 may comprise:

-   -   a first inlet 541 into the wet feed heat exchanger 545 in fluid         communication with the supply conduit for the wet hydrocarbon         stream 510;     -   a first outlet 549 from the wet feed heat exchanger 545 in fluid         communication with a first inlet 551 of the water removal device         525, which first outlet 549 is connected to the first inlet 541         through the wet feed heat exchanger 545;     -   a second inlet 561 into the wet feed heat exchanger 545 in fluid         communication with the vapour outlet 559 of the water removal         device 525;     -   a second outlet 569 from the wet feed heat exchanger 545 in         fluid communication with the first inlet 531 of the further heat         exchanger 535, which second outlet 569 is connected to the         second inlet 561 through the wet feed heat exchanger 545.

The water removal device 525 may be of any suitable known type. It may typically comprise a separator vessel for separating precipitated components from the wet hydrocarbon stream 510, and downstream thereof a water sorbing device for absorbing or adsorbing remaining water components from the residue vapour from which the precipitated components have been removed. Common in the field are solid bed dehydration units, also referred to as dry desiccant dehydration units. Typically, multiple beds are in use in a cyclic mode of operation involving drying (absorbing or adsorbing) and regeneration (desorbing). Preferably, the water sorbing device is also capable of removing mercury from the wet hydrocarbon stream, which can be facilitated by an appropriate selection of the sorbent employed in the solid bed.

The auxiliary heat exchanging arrangement 575 functions to further lower the temperature of the wet hydrocarbon stream 510 to facilitate the drying. In

FIGS. 1 and 2, the auxiliary heat exchanging arrangement 575 is embodied in the form of a water removal heat exchanger arranged between the first outlet 549 from the wet feed heat exchanger 545 and the first water removal device inlet 551 into the water removal device 525. Herewith heat can be extracted from the wet hydrocarbon stream 510 between the first outlet 549 from the wet feed heat exchanger 545 and the first water removal device inlet 551 into the water removal device 525.

Preferably the part 210 of the source refrigerant stream 280 is passed to the further heat exchanger 535 while maintaining its temperature essentially equal to the third temperature. To this end, it will not be passed through a deliberate heat exchanger and no heat exchanging with another medium will be taking place other than de-minimis unavoidable heat exchanging with the environment via the piping used for line 210. In practice this may mean that the temperature of the part 210 of the source refrigerant stream 280 that passes through the second tube bundle inlet 211 is less than 5° C. different, preferably less than 2° C. different, from the temperature of the source refrigerant stream 280 as it is discharged from the refrigerant condenser 285.

Preferably, the temperature of the part 210 of the source refrigerant stream, as it passes through the second tube bundle inlet 211 in the further heat exchanger 535, is within 10° C. from the first temperature. One way of achieving this is by passing the refrigerant through the refrigerant condenser 285 and heat exchanging it against the same type of ambient stream as the wet hydrocarbon stream 510. While it is possible to install a further heat exchanger in the effluent stream 560 between the wet feed heat exchanger 545 and the further heat exchanger 535 in order to even better approach the first temperature and/or the third temperature, for reasons of capital expenditure control and operational simplicity it is preferred that the temperature of the effluent stream 560 in the first tube bundle inlet 531 is essentially the same as the temperature of the effluent stream 560 that was reached by the indirectly heat exchanging against the wet hydrocarbon stream 510 in the wet feed heat exchanger 545. To this end, the first connecting means is preferably essentially free from any separate heat exchanger between the wet feed heat exchanger 545 and the first tube bundle inlet 531 of the further heat exchanger 535. The effluent stream 560 that is discharged from the wet feed heat exchanger 545 is thus preferably not passed through any deliberate heat exchanger, and no heat exchanging with another medium will be taking place other than de-minimis unavoidable heat exchanging with the environment via the piping used for the connection between the wet feed heat exchanger 545 and the first tube bundle inlet 531 of the further heat exchanger 535. In practice this may mean that the temperature of the effluent stream 560 that passes through the first tube bundle inlet 531 is less than 5° C. different, preferably less than 2° C. different, from the temperature of the effluent stream 560 as it is discharged from the wet feed heat exchanger 545.

Both the effluent stream 560 and the part 210 of the source refrigerant stream 280 that is passed to the further heat exchanger 535 are cooled in the further heat exchanger 535, by indirect heat exchanging against an evaporating refrigerant fraction 230. The evaporating refrigerant fraction is passed into the shell side of the further heat exchanger 535 via the shell inlet 231. The evaporating refrigerant may be a separate refrigerant from the part of the source refrigerant in line 210 that is being cooled. However, as shown in FIG. 1, it may be a part or all of the cooled refrigerant 220 that exits the further heat exchanger 535 via the second tube bundle outlet 219 into line 220. In the embodiments of FIGS. 1 and 2, the evaporating refrigerant fraction 230 is obtained by expanding at least a part of the cooled refrigerant 220 with the first expansion device 225. Optionally, a remaining part of the cooled refrigerant is passed to another heat exchanger (not shown) in the form of continuing refrigerant stream 235 to be evaporated at a lower pressure than the evaporating refrigerant fraction 230.

Preferably the temperature of the effluent stream 560 as admitted into the further heat exchanger 535 via the first tube bundle inlet 531 is within less than 10° C., preferably within less than 5° C., different from the temperature of the part 210 of the source refrigerant stream 280 as it is admitted into the further heat exchanger 535 via the second tube bundle inlet 211.

The expanded auxiliary refrigerant stream 260 is passed into the auxiliary heat exchanging arrangement 575 and discharged from the same after it has extracted heat from the wet hydrocarbon stream 510. The discharged auxiliary refrigerant 265 is recompressed.

The spent refrigerant 240 may be discharged from the further heat exchanger at a fourth temperature. The discharged auxiliary refrigerant stream 265 immediately after indirectly heat exchanging the discharged auxiliary refrigerant stream 265 against the wet hydrocarbon stream may be at a fifth temperature. The fifth temperature may be lower than the forth temperature. The direct heat exchanging of the discharged auxiliary refrigerant stream 265 will then cause vaporization of remaining liquid that might be present in the discharged auxiliary refrigerant stream 265 before the discharged auxiliary refrigerant stream 265 reaches the refrigerant compressor 270 for the first time after having been discharged from the auxiliary heat exchanging arrangement 575.

Preferably, the auxiliary refrigerant stream flow rate with which the auxiliary refrigerant stream 250 flows is less than 10% of the spent refrigerant stream flow rate with which the spent refrigerant stream 240 flows. The excess of the spent refrigerant stream 240 compared to the auxiliary refrigerant stream helps with the evaporation of remaining liquid that might be present in the discharged auxiliary refrigerant stream 265.

In FIGS. 1 and 2, the discharged auxiliary refrigerant 265 passes through the same optional suction drum 263 as the spent refrigerant in line 240. This way only a single suction drum 263 can handle both streams. Direct heat exchanging between the discharged auxiliary refrigerant 265 and the spent refrigerant 240 can take place either in a combined connection line 267 spanning between the combiner 266 and the suction drum 263 or in the suction drum 263, or both. The refrigerant compressor vapour feed stream 268 drawn from the suction drum 263 would thus contain all vapour from both the discharged auxiliary refrigerant 265 and the spent refrigerant 240. The refrigerant compressor vapour feed stream is fed into the refrigerant compressor 270 via a suction inlet 271 without condensing any part of the refrigerant compressor vapour feed stream 268 during any single pass from the suction drum 263 to the refrigerant compressor 270. The embodiments of FIGS. 1 and 2 are most suitable if the pressures of the spent refrigerant 240 and the discharged auxiliary refrigerant 265 are equal or substantially equal to each other.

FIG. 3 illustrates an alternative, suitable in case the discharged auxiliary refrigerant 265 is at a higher pressure than the spent refrigerant 240. In this case, the refrigerant compressor 270 should be a multi-stage compressor. The spent refrigerant 240 may be fed, optionally via the suction drum (not shown), to a second suction inlet 272 of the refrigerant compressor 270 after which it is compressed in two or more stages. At a transition between two successive stages of compression, the spent refrigerant is discharged from the refrigerant compressor 270 via an inter-compressed outlet 278 and led to combiner 266 wherein the spent refrigerant is combined with the discharged auxiliary refrigerant 265. Direct heat exchanging between the discharged auxiliary refrigerant 265 and the spent refrigerant 240 can take place either in the combined connection line 267, which in this embodiment spans between the combiner 266 and the suction inlet 271 of a subsequent compression stage in the refrigerant compressor 270. The vapour consisting of both the discharged auxiliary refrigerant 265 and the spent refrigerant 240 can thus further compressed and discharged from the refrigerant compressor 270 via the discharge outlet 279.

In the embodiment of FIG. 3 it is expected that the temperature of the spent refrigerant stream 240 in the combiner 266 is higher than in the case of the embodiments of FIGS. 1 and 2 because the spent refrigerant stream 240 will have picked up heat of compression. This will be extra heat that can be added to the discharged auxiliary refrigerant 265 to vaporize more residual liquid phase, which may be present in the discharged auxiliary refrigerant, than in the embodiments of FIGS. 1 and 2. Moreover, the direct heat exchanging taking place in the combined connection line 267 acts as an “intercooler” cooling the intermediately compressed spent refrigerant 240 between two successive stages of compression. The pressure in the second suction inlet 272 is between the suction pressure at the suction inlet 271 and the discharge pressure in discharge outlet 279. The discharge outlet 279 is fluidly connected to the source refrigerant line 280. The refrigerant stream in compressed condition is discharged from the discharge outlet 279, which refrigerant stream in compressed condition becomes the source of refrigerant 280 in the same way as described above.

A further optional feature illustrated in FIGS. 1 and 2 is that more than one refrigerant stream may be fed into the further heat exchanger 535. As can be seen in

FIGS. 1 and 2, the further heat exchanger 535 may additionally be provided with an optional third tube bundle inlet 311 for receiving another refrigerant stream 310. The third tube bundle inlet 311 is, via an optional third tube bundle 312 which may optionally be disposed inside the further heat exchanger 535, connected to a third tube bundle outlet 319 via which the cooled other refrigerant stream is discharged into line 320.

The cooled other refrigerant stream 320 may be partially or fully condensed in the further heat exchanger 535.

The cooled other refrigerant stream 320 may for instance be passed to another heat exchanger (not shown) to perform cooling duty therein. In performing said cooling duty, part of the condensed other refrigerant stream 320 may be evaporated in the other heat exchanger.

In one group of embodiments, as illustrated in FIG. 2, the other refrigerant stream 310 may form part of the same refrigerant circuit 200 as the source refrigerant stream 280. The refrigerant circuit in this group of embodiments may comprise a pre-cooling refrigerant gas/liquid separator 275 of which the overhead vapour outlet discharges into third tube bundle inlet 311 and of which pre-cooling refrigerant gas/liquid separator 275 the bottom liquid outlet discharges to the splitter 245. In this group of embodiments, the other refrigerant stream 310, after having been condensed to from the condensed other refrigerant stream 320 and evaporated in the other heat exchanger, may be returned to the refrigerant compressor 270 via an optional line 390 and an optional third suction inlet 273 into the refrigerant compressor 270. This is also illustrated in FIG. 2.

In another group of embodiments, the other refrigerant stream 310 may be circulated in another refrigerant circuit (not shown) that is separate from the discussed refrigerant circuit 200. For example, the refrigerant circuit 200 may be a pre-cooling refrigerant circuit used to produce the cooled hydrocarbon stream 540 and the cooled other refrigerant stream 320 in the form of a pre-cooled main refrigerant stream. The main refrigerant of the main refrigerant stream may be cycled in main refrigerant circuit that is distinct from the pre-cooling refrigerant circuit, such as described in for instance U.S. Pat. No. 6,370,910. In such a case, each of the pre-cooling refrigerant and the main refrigerant may be composed of a mixed refrigerant. A mixed refrigerant or a mixed refrigerant stream as referred to herein comprises at least 5 mol % of two different components. More preferably, any mixed refrigerant comprises two or more of the group consisting of: methane, ethane, ethylene, propane, propylene, butanes and pentanes.

Suitably, the pre-cooling refrigerant has a higher average molecular weight than main refrigerant. More specifically the pre-cooling refrigerant in the pre-cooling refrigerant circuit may be formed of a mixture of two or more components within the following composition: 0-20 mol % methane, 20-80 mol % ethane and/or ethylene, 20-80 mol % propane and/or propylene, <20 mol % butanes, <10 mol % pentanes; having a total of 100%. The main cooling refrigerant in the main refrigerant circuit may be formed of a mixture of two or more components within the following composition: <10 mol % N₂, 30-60 mol methane, 30-60 mol % ethane and/or ethylene, <20 mol % propane and/or propylene and <10% butanes; having a total of 100%.

Alternatively, and one embodiment employing this is illustrated in FIG. 2, the pre-cooling refrigerant and the main refrigerant may both be drawn from the refrigerant circuit 200. An example is the so-called Single Mixed Refrigerant processes, of which an example can be found in U.S. Pat. No. 5,832,745. In such a single mixed refrigerant process, the refrigerant being cycled in the refrigerant circuit may be formed of a mixture of two or more components within the following composition: <20 mol % N₂, 20-60 mol % methane, 20-60 mol % ethane and/or ethylene, <30 mol % propane and/or propylene, <15% butanes and <5% pentanes; having a total of 100%.

In the embodiment of FIG. 2 the source refrigerant stream 280 is partially, not fully, condensed (for instance in refrigerant condenser 285), and subsequently separated in a pre-cooling refrigerant gas/liquid separator 275 into a vaporous light fraction refrigerant stream and a liquid refrigerant. The vapour light refrigerant stream is discharged at the top of the pre-cooling refrigerant gas/liquid separator 275 into line 310 to be fed to the further heat exchanger 535 via the third tube bundle inlet 311 as the other refrigerant stream. The liquid refrigerant is discharged at the bottom of the pre-cooling refrigerant gas/liquid separator 275 and fed to the splitter 245 wherein it is split into the auxiliary refrigerant stream 250 and the part 210 of the source refrigerant stream 280.

As illustrated in FIG. 2, optionally a part of the condensed other refrigerant stream 320 may be injected into the evaporating refrigerant fraction 230 via optional line 352, optional third expansion device 353 (which may be provided in the form of a Joule-Thomson valve) and an optional combiner 357 provided in line 230.

In any case, the cooled hydrocarbon stream 540 that is discharged from the further heat exchanger 535 may be further treated in a variety of manners. In one group of embodiments, it may be cooled in one or more other heat exchangers against one or both of at least a part of the continuing refrigerant stream 235 being evaporated in another heat exchanger at a lower pressure than the evaporating refrigerant fraction 230 and at least a part of the cooled other refrigerant stream 320. Preferably, at least part of the cooled hydrocarbon stream 540 is cooled to a temperature low enough, such as below −125° C. or preferably below −150° C., to form liquefied natural gas. Such liquefied natural gas be depressurized in an end-flash system or depressurization stage as known in the art, and subsequently stored in a cryogenic liquid storage tank at a pressure of between 1 and 2 bar absolute and a temperature of approximately −162° C. This will not be described in further detail herein.

In another group of embodiments, the cooled hydrocarbon stream 540 may be subjected to one or more extraction steps wherein C₂+ hydrocarbons, preferably C₃+ hydrocarbons, are extracted from the cooled hydrocarbon stream 540 thereby generating a residue in the form of a methane-enriched hydrocarbon stream. This methane-enriched hydrocarbon stream may be sold as pipe line gas, or subjected to more cooling in the way described in the preceding paragraph, to produce liquefied natural gas. The extracted C₂+ hydrocarbons, preferably C₃+ hydrocarbons, may be sold and/or further processed, for instance by fractionation into single-component streams including ethane and/or propane and/or butane.

The person skilled in the art will understand that the present invention can be carried out in many various ways without departing from the scope of the appended claims. 

1. Method of treating a hydrocarbon stream comprising methane, the method comprising: providing a wet hydrocarbon stream at a first temperature, said wet hydrocarbon stream comprising at least methane and water; cooling of the wet hydrocarbon stream thereby lowering the temperature from the first temperature to a second temperature, wherein said cooling of the wet hydrocarbon stream comprises indirectly heat exchanging against an effluent stream followed by indirectly heat exchanging against an auxiliary refrigerant stream; withdrawing from the wet hydrocarbon stream, in a water removal device at the second temperature, a wet disposal stream comprising water from the wet hydrocarbon stream and an effluent stream comprising the wet hydrocarbon stream from which the wet disposal stream has been removed; passing the effluent stream to a further heat exchanger, said passing of the effluent stream to the further heat exchanger comprising heating the effluent stream by indirectly heat exchanging against the wet hydrocarbon stream in a wet feed heat exchanger; cooling the effluent stream in the further heat exchanger by indirect heat exchanging against an evaporating refrigerant fraction; cycling a refrigerant in repetitive cycles, wherein a single pass of the refrigerant through the cycle comprises the following consecutive steps: providing a refrigerant stream in a compressed condition; passing the refrigerant stream in said compressed condition through a condenser whereby at least partially condensing the refrigerant stream in said compressed condition, thereby forming source refrigerant stream comprising a liquid phase at a refrigerant temperature and a refrigerant pressure; obtaining the evaporating refrigerant fraction comprising expanding at least a part of a part of the source refrigerant stream to a pressure lower than the refrigerant pressure; passing the evaporating refrigerant fraction to the further heat exchanger; forming a spent refrigerant from the evaporating refrigerant fraction by absorbing heat from at least the effluent stream in the further heat exchanger; discharging said spent refrigerant from the further heat exchanger; passing said spent refrigerant to a refrigerant compressor; discharging from the refrigerant compressor said refrigerant stream in compressed condition; wherein during said single pass the cycle further comprises the following consecutive steps: splitting the source refrigerant stream into said auxiliary refrigerant stream and said part of the source refrigerant stream wherein said auxiliary refrigerant stream comprises at least a part of said liquid phase; indirectly heat exchanging the auxiliary refrigerant stream against said wet hydrocarbon stream whereby passing heat from the wet hydrocarbon stream to the auxiliary refrigerant stream as part of said cooling of the wet hydrocarbon stream whereby discharging a discharged auxiliary refrigerant stream containing said heat from the wet hydrocarbon stream; directly heat exchanging the discharged auxiliary refrigerant stream with the spent refrigerant being passed to the refrigerant compressor; forming the refrigerant stream in compressed condition by compressing the spent refrigerant and the discharged auxiliary refrigerant stream whereby allowing said direct heat exchanging before said compressing in each single pass.
 2. The method according to claim 1, wherein said condenser is provided in the form of an ambient heat exchanger and wherein providing of the wet hydrocarbon stream comprises passing said wet hydrocarbon stream through a wet feed ambient heat exchanger thereby heat exchanging said wet hydrocarbon stream against ambient and thereby providing the wet hydrocarbon stream at said temperature equal to the first temperature; and wherein said condensing of said refrigerant stream in said compressed condition comprising heat exchanging said refrigerant stream in said compressed condition against ambient, thereby providing said source refrigerant stream at a refrigerant temperature equal to a third temperature, which is within 10° C. from the first temperature.
 3. The method according to claim 2, further comprising: admitting the effluent stream into the further heat exchanger via a first tube bundle inlet; and wherein said obtaining of said evaporating refrigerant fraction during said single pass of the refrigerant through the cycle comprises: passing said part of the source refrigerant stream to the further heat exchanger while maintaining its temperature essentially equal to the third temperature; admitting the part of the source refrigerant stream into the further heat exchanger via least one second tube bundle inlet; and cooling the part of the refrigerant stream in the further heat exchanger against the evaporating refrigerant fraction; followed by said expanding.
 4. The method according to claim 3, wherein the temperature of the effluent stream in the first tube bundle inlet is essentially the same as the temperature of the effluent stream that was reached by said indirectly heat exchanging against the wet hydrocarbon stream at essentially said first temperature in the wet feed heat exchanger, and wherein the temperature of the effluent stream and the temperature of the part of the source refrigerant stream in the first and second tube bundle inlets in the further heat exchanger are less than 10° C. apart from each other.
 5. The method according to claim 1, wherein during said single pass after said splitting and before said indirectly heat exchanging of the auxiliary refrigerant stream against said wet hydrocarbon stream, the auxiliary refrigerant stream is expanded.
 6. The method according to claim 1, wherein the temperature of the effluent stream is matched to the first temperature as close as the warm end approach temperature of the wet feed heat exchanger by said heating of the effluent stream by indirectly heat exchanging against the wet hydrocarbon stream in the wet feed heat exchanger during said passing of the effluent stream to the further heat exchanger.
 7. The method according to claim 1, wherein the water removal device comprises a separator vessel for separating precipitated components from the wet hydrocarbon stream and, downstream thereof, a sorbing device sorbing at least water.
 8. The method according to claim 1, wherein the first temperature of the wet hydrocarbon stream, before said indirect heat exchanging against the effluent stream, is controlled by heat exchanging against said ambient stream; and wherein the at least part of the source refrigerant stream has a temperature within 10° C. from the first temperature.
 9. The method according to claim 1, wherein said directly heat exchanging of the discharged auxiliary refrigerant stream with the spent refrigerant comprises injecting the discharged auxiliary refrigerant stream into the spent refrigerant being passed from the further heat exchanger to the refrigerant compressor.
 10. The method according to claim 9, further comprising passing the discharged auxiliary refrigerant stream and the spent refrigerant both through a single suction drum, drawing from the suction drum a refrigerant compressor vapour feed stream and passing the refrigerant compressor vapour feed stream to the refrigerant compressor without condensing any part of the refrigerant compressor vapour feed stream during any single pass from the suction drum to the refrigerant compressor.
 11. The method according to claim 1, wherein the spent refrigerant is discharged from the further heat exchanger at a fourth temperature and wherein the discharged auxiliary refrigerant stream immediately after its indirectly heat exchanging against the wet hydrocarbon stream is at a fifth temperature, wherein said fifth temperature is lower than the forth temperature.
 12. The method according to claim 1, wherein the auxiliary refrigerant stream flows at an stream flow rate and wherein the spent refrigerant stream flows at a spent refrigerant stream flow rate, wherein the auxiliary refrigerant stream flow rate is less than 10% of the spent refrigerant stream flow rate.
 13. The method according to claim 1, wherein the wet hydrocarbon stream comprises natural gas, and wherein at least part of the effluent stream is cooled to form liquefied natural gas.
 14. Apparatus for treating a hydrocarbon stream comprising methane, the apparatus comprising: a supply conduit for providing a wet hydrocarbon stream that comprises at least methane and water; a wet feed heat exchanger connected to the supply conduit, and arranged to receive the wet hydrocarbon stream from the supply conduit, and to lower the temperature of the wet hydrocarbon stream by indirect heat exchanging against an effluent stream; an auxiliary heat exchanging arrangement arranged to further lower the temperature of the wet hydrocarbon stream discharged from the wet feed heat exchanger by indirect heat exchanging against an auxiliary refrigerant stream; a water removal device, arranged to receive the wet hydrocarbon stream downstream of the auxiliary heat exchanging arrangement, and comprising a wet disposal stream outlet for discharging a wet disposal stream comprising water from the wet hydrocarbon stream, and a vapour outlet for discharging an effluent stream comprising the wet hydrocarbon stream from which the wet disposal stream has been removed; a further heat exchanger provided with a first tube bundle inlet for receiving the effluent stream from the water removal device, and a first tube bundle outlet for discharging a cooled hydrocarbon stream, wherein the first tube bundle outlet is internally in the further heat exchanger connected with the first tube bundle inlet via a first tube bundle, and wherein said first tube bundle is arranged in a heat exchanging relationship with an evaporating refrigerant fraction inside the further heat exchanger; first connecting means connecting the vapour outlet of the water removal device with the first tube bundle inlet of the further heat exchanger, which first connecting means passes through the wet feed heat exchanger in indirect heat exchanging interaction with the wet hydrocarbon stream; a refrigerant circuit arranged to cycle a refrigerant in repetitive cycles, said refrigerant circuit, when being considered following the flow of the refrigerant during a single pass through the refrigerant circuit starting from a discharge outlet of a refrigerant compressor, comprising: a condenser arranged to receive a refrigerant stream in a compressed condition and to extract heat from the refrigerant stream in said compressed condition whereby at least partially condensing the refrigerant stream in said compressed condition thereby forming a source refrigerant stream comprising a refrigerant stream in a compressed condition and comprising a liquid phase; a first expansion device arranged to receive and expand at least a part of a part of the source refrigerant stream thereby obtaining the evaporating refrigerant fraction; the further heat exchanger arranged to receive the evaporating refrigerant fraction from the first expansion device, in which further heat exchanger a cooling zone is provided wherein the evaporating refrigerant fraction is arranged in indirect heat exchanging contact with at least the effluent stream in the first tube bundle whereby the evaporating refrigerant fraction is transformed into spent refrigerant, said further heat exchanger comprising a shell outlet to discharge the spent refrigerant from the cooling zone; a spent refrigerant line connecting the shell outlet to the refrigerant compressor, the discharge outlet of the refrigerant compressor arranged to discharge said refrigerant stream in said compressed condition; a splitter, arranged to split the source refrigerant stream into the auxiliary refrigerant stream and the part of the source refrigerant stream, wherein said auxiliary refrigerant stream comprises at least a part of said liquid phase; a combiner arranged to bring the spent refrigerant and a discharged auxiliary refrigerant consisting of the auxiliary refrigerant discharged from the auxiliary heat exchanging arrangement together in direct heat exchanging contact, whereby the auxiliary heat exchanging arrangement is arranged in the auxiliary refrigerant stream between the splitter and the combiner, said combiner being between the auxiliary heat exchanging arrangement and the refrigerant compressor, wherein said refrigerant stream in compressed condition contains both the discharged auxiliary refrigerant stream and the spent refrigerant stream.
 15. The apparatus according to claim 14, further comprising: a wet feed ambient heat exchanger arranged in the supply conduit arranged to receive the wet hydrocarbon stream and to exchange heat between the wet hydrocarbon stream and an ambient stream wherein the wet feed heat exchanger is connected to the supply conduit via the wet feed ambient heat exchanger, wherein there is essentially no separate heat exchanger present between the wet feed ambient heat exchanger and the wet feed heat exchanger; wherein the first connecting means is essentially free from any separate heat exchanger between the wet feed heat exchanger and the first tube bundle inlet of the further heat exchanger; wherein said condenser is provided in the form of an ambient heat exchanger; wherein the further heat exchanger is further provided with at least one second tube bundle outlet for discharging at least one cooled refrigerant stream, wherein the at least one second tube bundle outlet is internally in the further heat exchanger connected with the second tube bundle inlet via a second tube bundle arranged in the cooling zone; second connecting means connecting the condenser with the second tube bundle inlet, for receiving at least the part of said source refrigerant stream, said second connecting means being essentially free from any separate heat exchanger. 